See "Best Practices: Competing Online" for more detailed troubleshooting tips.
You have to be using an up-to-date version of Google Chrome. If testing from their home, should check router setup to ensure nothing internally is blocking the connection. If at a workplace/school, a firewall may be causing an issue.
While a desktop or laptop computer will be most reliable, on mobile devices and Chromebooks – including tablets – download the Jitsi videoconference app. Once that is loaded on your device, when clicking the camera icon to enter an NSDA Campus room, it will automatically load in Jitsi.
Finally, it may help to clear the browser cache. I would then suggest switching to another device if possible to see if it fixes the issue if nothing else does.